Optics for chip-on-board road and area lighting

ABSTRACT

A lamp includes an extended planar light source, and an optical element arranged with the light source, wherein the optical element comprises an outer surface having an indented cusp substantially over the light source. A lamp includes an extended planar light source, and an optical element arranged with the light source, wherein the optical element comprises an outer surface having a portion at a peripheral edge comprising a curvature configured to redirect light emitted from the light source by total internal reflection.

FIELD

The present application relates generally to light emitting diode(LED)-based illumination, and more particularly, to street and arealighting using chip-on-board (COB) LED lighting sources.

BACKGROUND

Street lighting luminaires generate light patterns that may be evaluatedin a classification system known as BUG, for Backlight, Uplight andGlare. BUG is a reference tool, and other metrics may exist tocharacterized street light performance with respect to an angularaltitude direction from vertical down, where upward pointing light has adirection angle from 90° up to 180°, and whether light is directedtoward an intended area of illumination or outside at altitude anglesfrom 0° to 90°, as well as azimuth direction in a horizontal plane.

Glare may be generally termed as downward directed light pointing in theintended illumination direction but which may also produce annoying orvisually disabling levels of light. Backlight creates generally downwardpointing light trespassing onto adjacent sites that may be illuminatedby other luminaires, or is altogether undesirable illumination. To acertain extent, Backlight is wasteful and/or undesirable. Uplight isundesirable artificial skyglow, which may adversely affect astronomywith backscattered light pollution, and is mostly wasted energy. Controlof the beam pattern and intensity produced by a luminaire may depend atleast on the type of light source selected, focusing and redirection ofemitted light, including, but not limited to, the use of reflectors,optical correction (e.g., lenses), and shielding (e.g., chimney- ortunnel-type restrictors).

One type of light source is a light emitting diode (LED), which maytypically produce satisfactory levels of light intensity at power levelslower than may be needed for incandescent, vapor glow or other lightsources. A light emitting diode comprises a semiconductor materialimpregnated, or doped, with impurities. These impurities add “electrons”and “holes” to the semiconductor, which can move in the materialrelatively freely. Depending on the kind of impurity, a doped region ofthe semiconductor can have predominantly electrons or holes, and isreferred to as an n-type or p-type semiconductor region, respectively.

In LED applications, an LED semiconductor chip includes an n-typesemiconductor region and a p-type semiconductor region. A reverseelectric field is created at the junction between the two regions, whichcauses the electrons and holes to move away from the junction to form anactive region. When a forward voltage sufficient to overcome the reverseelectric field is applied across the p-n junction, electrons and holesare forced into the active region and combine. When electrons combinewith holes, they fall to lower energy levels and release energy in theform of light. The ability of LED semiconductors to emit light hasallowed these semiconductors to be used in a variety of lightingdevices. For example, LED semiconductors may be used in general lightingdevices for interior applications or in various exterior applications.

During manufacture, an array comprising a large number of LEDsemiconductor devices (or dies) are produced on a substrate.Chip-on-board (COB) lights include multiple LED chips packaged togetheras one lighting module forming a large effective emitting surface,giving the appearance of an “extended” light source. In comparison to asingle die (i.e., single chip) LED, which approximates a point source,it is more difficult to design optical lenses for use with large COBLEDs to control the illumination light pattern projected for streetlighting to avoid undesirable glare, backlight and uplight. It may begenerally desirable to limit glare, for example, beyond 60°-70°, andsomewhat similarly for backlight, so as to avoid undesirableillumination, such as may be directed toward residential windows

Accordingly, what is needed is a lens design for COB LEDs that formhighly efficient optical beam patterns for various applicationsincluding street lighting that limit light pollution.

SUMMARY

In an aspect of the disclosure, a lamp includes a light source, and anoptical element having an index of refraction greater than 1, whereinthe optical element includes an inner surface arranged opposite thelight source, and an outer surface of varying curvature originating froma single point above the light source to an edge of the optical element,wherein a portion of the outer surface at a peripheral edge of theoptical element is configured to redirect light emitted from the lightsource by total internal reflection.

In an aspect of the disclosure, a luminaire optical assembly emittinglight in a confined beam pattern includes a light source, a lens havingan index of refraction greater than 1 comprising an inner surfacearranged to face the light source, an outer surface of varying curvatureoriginating from a single point above the light source to an edge of theoptical element, wherein a portion of the outer surface at a peripheraledge of the optical element is configured to redirect light emitted bythe light source by total internal reflection into a confined beampattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating a COB LED arranged within a complexlens in accordance with the disclosure.

FIG. 2 is a perspective view illustrating the COB LED arranged withinthe complex lens of FIG. 1 in accordance with the disclosure.

FIG. 3 is a side-view illustrating a long dimension of the complex lensarranged with the COB LED of FIG. 1 in accordance with the disclosure.

FIG. 4 is a side-view illustrating a view of in a width directionperpendicular to the long direction of the complex lens arranged withthe COB LED of FIG. 1 in accordance with the disclosure.

FIG. 5A is a perspective view of one embodiment of the complex lens ofFIG. 1 with added features for redirecting light emitted by the COB LEDin accordance with the disclosure.

FIG. 5B is a perspective view of a second embodiment of a complex lenswith added features for redirecting light emitted by the COB LED inaccordance with the disclosure.

FIG. 5C is a perspective view of a third embodiment of a complex lenswith added features for redirecting light emitted by the COB LED inaccordance with the disclosure.

FIG. 6 is a representation of an application of a street lamp as anexample of a luminaire optical assembly 600 that may include a COB LEDand complex optic in accordance with the disclosure.

DESCRIPTION

In various aspects, a lens is provided for desirably controlling a lightdistribution pattern of light emitted by a COB LED. The resulting lightpattern has clear boundaries, where light intensity decreases quicklybeyond the intended area of illumination.

The present invention is described more fully hereinafter with referenceto the accompanying Drawings, in which various aspects of the presentinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to the variousaspects presented throughout this disclosure. Rather, these aspects areprovided so that this disclosure will be complete enough to provide athorough understanding of the present invention to those skilled in theart. The various aspects of the present invention illustrated in thedrawings may not be drawn to scale. Accordingly, the dimensions of thevarious features may be expanded or reduced for clarity. In addition,some of the drawings may be simplified for clarity. Thus, the drawingsmay not depict all of the components of a given apparatus (e.g., device)or method.

Various aspects of the present invention will be described herein withreference to drawings that are schematic illustrations of idealizedconfigurations of the present invention. As such, variations from theshapes of the illustrations as a result, for example, manufacturingtechniques and/or tolerances, are to be expected. Thus, the variousaspects of the present invention presented throughout this disclosureshould not be construed as limited to the particular shapes of elements(e. g., regions, layers, sections, substrates, etc.) illustrated anddescribed herein but are to include deviations in shapes that result,for example, from manufacturing. By way of example, an elementillustrated or described as a rectangle may have rounded or curvedfeatures and/or a gradient concentration at its edges rather than adiscrete change from one element to another. Thus, the elementsillustrated in the drawings are schematic in nature and their shapes maynot be intended to illustrate the precise shape of an element and arenot intended to limit the scope of the present disclosure.

It will be understood that when an element such as a region, layer,section, substrate, or the like, is referred to as being “on” anotherelement, it can be directly on the other element or intervening elementsmay also be present. In contrast, when an element is referred to asbeing “directly on” another element, there are no intervening elementspresent. It will be further understood that when an element is referredto as being “formed” on another element, it can be grown, deposited,etched, attached, connected, coupled, or otherwise prepared orfabricated on the other element or an intervening element.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the drawings. It will be understoodthat relative terms are intended to encompass different orientations ofan apparatus in addition to the orientation depicted in the Drawings. Byway of example, if an apparatus in the Drawings is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on the “upper” sides of the other elements. The term “lower”,can therefore, encompass both an orientation of “lower” and “upper,”depending of the particular orientation of the apparatus. Similarly, ifan apparatus in the drawing is turned over, elements described as“below” or “beneath” other elements would then be oriented “above” theother elements. The terms “below” or “beneath” can, therefore, encompassboth an orientation of above and below.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andthis disclosure.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. The term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that although the terms “first” and “second” maybe used herein to describe various regions, layers and/or sections,these regions, layers and/or sections should not be limited by theseterms. These terms are only used to distinguish one region, layer orsection from another region, layer or section. Thus, a first region,layer or section discussed below could be termed a second region, layeror section, and similarly, a second region, layer or section may betermed a first region, layer or section without departing from theteachings of the present invention.

FIG. 1 shows a plan view of an exemplary arrangement of a complex lens100 arranged with an extended planar light sourced, which may be, forexample, a COB LED 110. The complex lens 100 includes a flange 120surrounding the COB LED 110 that may be used for fixing the complex lens100 to the COB LED 110. The complex lens 100 may be characterized by anouter surface 130 and an inner surface 160. The inner surface 160 of thecomplex lens 100 may be arranged over the COB LED 110, and may furtherbe symmetrically arranged with respect to the COB LED 110. The curvatureof the inner surface 160 may be, for example, bi-axially elliptical andsymmetrically positioned over the COB LED 110, however, other curvaturesand asymmetry may be considered within the scope of the disclosure.

The outer surface 130 of the complex lens 100 may be characterized by anindented cusp 135 at a single point. The cusp 135 may preferably belocated directly over the COB LED 110 and the inner surface 160 in asymmetrical configuration, however, other placements of the cusp 135 maybe considered within the scope of the disclosure. The cusp 135 may serveas an origin from which a plurality of loci 140 _(x) (x=−a, −b, . . . a,b, . . . , etc., where x denotes a value of azimuth angle φ) define asurface curvature of the outer surface and diverge toward the flange120. When viewed as shown in FIG. 1, the loci 140 x may change, e.g.,continuously, as a function of an azimuth angle φ. As shown in FIG. 1, awidthwise plane normal to a plane formed by the flange 120 and indicatedby a line 145. The azimuth angle φ may be specified with respect to thisline, where the single point 135 serves as an origin. Several loci 140_(a), 140 _(b), . . . 140 _(x), 140 _(−a), 140 _(−b), . . . 140 _(−x),etc., are shown for illustrative purposes in the plan view of FIG. 1,where a, b, . . . x indicate a value of the azimuth angle φ.

In one embodiment, the loci may generate a surface of curvature of theouter surface 130 that is mirror symmetric about the widthwise normalplane indicated by line 145, which includes the zero of azimuth, i.e.,angle φ=0°. That is, loci 140 _(x) and loci 140 _(−x) may besymmetrically mirrored across the widthwise normal plane indicated by aline 145 arranged in a widthwise.

In an embodiment where the COB LED 110 is placed centered and symmetricwith respect to the cusp 135, the inner surface 160 is shape symmetric(e.g., biaxially elliptic and also placed centered with respect to thecusp 135), it may be clear that the loci 140 _(x) form a surface ofcurvature of the outer surface 130 that is symmetric about the line 145.Furthermore, it may be clear from this arrangement that light emitted bythe light source will be emitted from the complex lens 100 through theouter surface 130 that is also symmetric with respect to the line 145.

For a line 146 defined by φ=±90°, where a plane normal to the flange 120is formed through the line 146, it may be seen that the complex lens 100has an outer curvature that is asymmetric with respect to the line 146arranged in a lengthwise direction. As a consequence, it may be seenthat light emitted from the COB LED 110 centered with respect to thecusp 135 forms an asymmetric beam with respect to the line 146.

FIG. 2 shows a perspective view of the complex lens 100 and COB LED 110showing the various features of the inner surface 160, outer surface130, lines 145 and 146, and exemplary loci of curvatures 140 _(a), 140_(b), 140 _(−a), 140 _(−b), of the outer surface 130. The overall lightdistribution of the light beam pattern produced is mainly controlled bythe surface curvature that forms the outer surface 130, the geometry ofthe inner surface 260 of the complex lens 100, a refractive index of thematerial included in the complex lens 100, and the geometry andemittance pattern of the COB LED 110. In an embodiment, the cusp 135,from which all loci 140 originate, may be, for example, an indentationwith an approximately conical surface region 236. Because it may occurthat the brightest illumination from the COB LED 110 may be directedtoward the single point 135 substantially along a vector direction 250normal to a plane containing the COB LED 110 and flange 120, theindentation provides a somewhat conical surface that may enablesufficient refraction and/or total internal reflection of light awayfrom the normal direction to maintain the emitted light intensity acrossthe beam within a certain range at, e.g., street level, i.e., to reduce“hot spots.”

The complex lens 100 may be characterized as transparent and having anoptical index of refraction n that is typically greater than air, i.e.,n>1. A typical optical index of refraction may be ˜1.5, but an actualvalue depends on the material from which the complex lens 100 is made.The index of refraction n and the shape and extent of the conical region236 determines the redirection of a portion of light emitted from theCOB 110 LED in the approximately normal direction away from the normalvector direction 250.

FIG. 3 shows a side-view cross-section of the complex lens 100 and COBLED 110 cut through the plane formed by the line 146 of FIG. 1. For thesake of illustration, the arrangement of the COB LED 110 and complexlens 100 are shown pointing so that light is emitted substantiallydownward, as would be the case in a street light luminaire. It may beseen that the cross-section of the arrangement of the complex lens 100and COB LED 110 is symmetric with respect to line 145. As a consequence,the projected light emission pattern is also substantially symmetricabout line 145. As shown in FIG. 3, light rays emitted at a high angleare strongly directed toward portions of the complex lens 100 adjacentto the flange 120. Light emitted in this direction, if emitted throughthe outer surface 130 at such locations, may contribute undesirably toGlare, Backlight, or potentially even Uplight. For this reason, thecurvature of the outer surface 130 at such locations may be inwardlycurved sufficiently to cause total internal reflection (TIR), accordingto Snell's Law, with the consequence of redirection of light incident atthat surface in a direction that is more normal (i.e., downward, in theillustration of FIG. 3), thereby reducing an amount of light that mayradiate sideways, in order to reduce Glare and Backlight.

FIG. 4 shows a cross-section side-view illustrating the complex lens 100and COB LED 110 cut through the plane formed by the line 145 of FIG. 1,and oriented to illuminate in a downward direction, as in FIG. 3. It maybe seen that the cross-section of the arrangement of the complex lens100 and COB LED 110 is asymmetric with respect to line 146. As aconsequence, the projected light emission pattern is also substantiallyasymmetric about line 146. As in the view shown in FIG. 3, light raysemitted at a high angle (not shown) are strongly directed towardportions of the complex lens 100 adjacent to the flange 120, whereagain, the curvature of the outer surface is inwardly curvedsufficiently to cause total internal reflection (TIR), with theconsequence again of redirection of light incident at that surface in adirection that is more normal to the plane of the flange 120 and COB LED110.

Referring to FIG. 3, in operation, high angle rays emitted by the COBLED 110 will be refracted by the inner surface 160 (toward the normaldirection of the inner surface 160, according to Snell's Law). The highangle rays intersect a portion of the outer surface 130 (e.g., adjacentor near the flange 120) at an angle beyond the critical angle for totalinternal reflection (TIR) and consequently are totally internallyreflected toward other areas of the outer surface 230 where the angle ofincidence is closer to normal, resulting in a portion of the light raybeing emitted through the outer surface in a direction that is moreusefully concentrated to the street and/or sidewalk. A beam shape of theemitted light, and the sharpness of the boundary between the brightregion of the beam, and a darker surrounding space outside the beam isdetermined by the detailed combination of the various loci of curvaturesof the inner surface 160, the outer curved surface 230, particularlynearer the flange 120, and the relative optical index n between (1) thecomplex lens 100 and the space inside the inner surface 260 (e.g., wherepresumably n_(air) ˜1) and (2) the region outside the outer curvedsurface 230 (again, e.g., presumably n_(air) ˜1).

FIG. 5A shows a perspective view of another embodiment of the complexlens 100. The angular distribution of the output rays coming out fromthe outer surface 130 of the complex lens 100 may be further modified orredistributed by means of additional features 510, 520 integrated withor added to the lens surfaces. The features 510, 520 may be reflective,diffractive, refractive scattering features and any combination thereof.The complex lens 100, and additional features 510, 520 may be any ofclear (i.e., optically transparent), semi-transparent, translucent,color tinted. Additionally, the complex lens may have a combination ofphosphors on either or both inner and outer surfaces 160, 130 to alter acolor balance of light emitted by the COB LED 110.

FIG. 5B shows several views of another embodiment of the complex lens100 wherein in the features 510, 520 may include designed indentationsin the outer surface 130 rather than being added outside the outersurface 130. Additionally, using an embodiment of this nature, thecurvature of the outer surface 130 at the intersection with the flange120 may not necessarily include undercuts to induce total internalreflection at this periphery, although such undercutting may beretained. An advantage of eliminating the indentation of the curvatureof the outer surface 130 at the flange 120 is an easier molding and moldremoval operation that does not have to deal with undercuts in thecomplex lens 100.

FIG. 5C shows several views of still another embodiment of the complexlens 100 wherein in the features 510, 520 may include designedindentations in the inner surface 160 rather than being added to theouter surface 130. In this embodiment the outer surface 130 is smooth,Furthermore, the outer surface 130 may be formed with or without theundercutting, as in the embodiment in FIG. 5B.

FIG. 6 is an example of an application of a street lamp as an example ofa luminaire optical assembly 600 that may include the COB LED 110 andcomplex optic 100. The luminaire optical assembly 600 may include a lamppole 610 and a head 620 attached to the pole 610. The head 620 mayinclude a lamp, which may include a light source. The light source maybe the COB LED 110. The lamp may include the complex optic 100configured to emit light from the COB LED 110 in a directed beam 630 toprovide an illumination and intensity pattern 635. Outside the pattern635 the intensity falls off to a lower level.

In another aspect, among the characteristics that may be taken intoaccount include the height 615 of the lamp pole 610, and theillumination pattern/intensity 635 sought for the application, which isdetermined at least by the combination of the COB LED 110, the index ofrefraction n and the details of curvature of the inner and outersurfaces 160, 130 of the complex lens 100.

In one aspect of a street light, the collimated light beam may emulate apoint source of light, which enables a light distribution pattern (e.g.,Type I, II, III, IV, or V, and may also be characterized by BUGdescription) to be determined by the design of the complex lens 100positioned below the COB LED 110 (e.g., planar LED array or other lightsource).

The street lamp of FIG. 6 is merely exemplary of one embodiment, and isnot to be construed as so limited, as the components may be arranged toform, for example, a free standing lamp or table lamp including the COBLED 110 and complex lens 100 to provide a light illumination pattern 635of a similar nature as described above.

FIG. 7 presents examples of luminous flux distribution of variousembodiments of the complex lens 100 as described in FIGS. 5A-5C. It maybe appreciated that the various embodiments, and combinations andvariations thereof, may realize uniform illumination at the target area,while satisfying criteria according to BUG classifications.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed as a means plus functionunless the element is expressly recited using the phrase “means for.”

1-23. (canceled)
 24. A lens for a light source comprising: an outersurface that is asymmetric in a first plane and that is symmetricrelative to a second that is perpendicular to the first plane; and anindented cusp disposed at an intersection of the respective planes ofthe outer surface, with the indented cusp forming an indented cone andbeing symmetrical about a plane that runs through a single point of theindented cusp.
 25. The lens according to claim 24, wherein the indentedcusp is constructed as an origin from which a plurality of loci define asurface curvature of the outer surface that diverge outward.
 26. Thelens according to claim 24, further comprising a flange that surroundsthe outer surface of the lens.
 27. The lens of claim 24, wherein theindented cusp forms the indented cone with a circular outer boundarythat extends towards a light source and forms a single point positionedover the light source.
 28. The lens of claim 24, wherein a portion ofthe outer surface at a peripheral edge comprises a curvature configuredto redirect light emitted from the light source by total internalreflection.
 29. The lens of claim 24, wherein the indented cusp isoffset from a center axis of the outer surface normal to a plane of thelight source.
 30. The lens of claim 24, wherein the outer surfacecomprises at least one of a refractive, diffractive, prismatic,scattering, semitransparent, and translucent surface.
 31. A lens for alight source comprising: a curved outer surface that is asymmetric withrespect to a plane in a first direction and that is symmetric withrespect to a plane in a second direction that intersects the firstdirection; and an indented cusp disposed in the outer surface where bothplanes intersect, with the indented cusp forming an indented cone with acircular outer boundary, wherein the indented cusp is symmetrical abouta plane that runs through a single point of the indented cusp, andwherein the indented cusp is constructed as an origin from which aplurality of loci define a surface curvature of the curved outer surfacethat diverge outward.
 32. The lens according to claim 31, furthercomprising a flange that surrounds the curved outer surface of the lens.33. The lens of claim 31, wherein the circular outer boundary of theindented cone extends towards a light source and forms a single pointpositioned over the light source.
 34. The lens of claim 31, wherein aportion of the curved outer surface at a peripheral edge comprises acurvature configured to redirect light emitted from the light source bytotal internal reflection.
 35. The lens of claim 31, wherein theindented cusp is offset from a center axis of the curved outer surfacenormal to a plane of the light source.
 36. The lens of claim 31, whereinthe curved outer surface comprises at least one of a refractive,diffractive, prismatic, scattering, semitransparent, and translucentsurface.
 37. A luminaire optical assembly emitting light in a directedbeam pattern comprising: a pole; a boom extending from the pole; a lampsupported at an end of the boom comprising: a light source; a curvedouter surface that is asymmetric with respect to a plane in a firstdirection and that is symmetric with respect to a plane in a seconddirection that intersects the first direction; and an indented cuspdisposed in the outer surface where both planes intersect, with theindented cusp forming an indented cone with a circular outer boundary,wherein the indented cusp is symmetrical about a plane that runs througha single point of the indented cusp, and wherein the indented cusp isconstructed as an origin from which a plurality of loci define a surfacecurvature of the curved outer surface that diverge outward.
 38. Theluminaire optical assembly according to claim 37, wherein the lampfurther comprises a flange that surrounds the curved outer surface ofthe lens.
 39. The luminaire optical assembly of claim 37, wherein thecircular outer boundary of the indented cone extends towards a lightsource and forms a single point positioned over the light source. 40.The luminaire optical assembly of claim 37, wherein a portion of thecurved outer surface at a peripheral edge comprises a curvatureconfigured to redirect light emitted from the light source by totalinternal reflection.
 41. The luminaire optical assembly of claim 37,wherein the indented cusp is offset from a center axis of the curvedouter surface normal to a plane of the light source.
 42. The luminaireoptical assembly of claim 37, wherein the curved outer surface comprisesat least one of a refractive, diffractive, prismatic, scattering,semitransparent, and translucent surface.